Spectroscopy is a science where a sample substance is analyzed by means of the spectra of light the sample absorbs or emits. Technological advancements in both wavelength-dispersive (WD-XRF) and energy-dispersive (ED-XRF) X-ray fluorescence instrumentation enable the spectroscopic analysis of virtually all types of sample materials. In this technology, sample cups or sample receptacles are employed to hold or contain liquid, solid and powdered specimens. Many conventional prior art sample cups consist of four components. The four components include a cell body with at least one open end; a thin film of material capable of covering the open end of the cell body; an annular collar used to pull the thin film of material taut over the open end of the cell body; and a snap-on retainer ring used to secure the thin film of material in place. The thin film of material encloses a sample substance within the cell body and provides a sample surface plane which is exposed to an excitation source, such as an X-ray tube, during the analysis. Such conventional prior art cups are exemplified by U.S. Pat. No. Des. 238,693 entitled “CELL FOR X-RAY SPECTROSCOPY OR SIMILAR ARTICLE” issued on Feb. 3, 1976 to Monte J. Solazzi; U.S. Pat. No. 4,409,854 entitled “SAMPLE CUP WITH VENTING MEANS FOR USE IN X-RAY SPECTROSCOPY” issued on Oct. 18, 1983 to Michael C. Solazzi; U.S. Pat. No. 4,643,033 entitled “SAMPLE CUP FOR USE IN X-RAY SPECTROSCOPY” issued on Feb. 17, 1987 to Monte J. Solazzi; U.S. Pat. No. 4,665,759 entitled “SAMPLE CUP WITH A CANTILEVER BEAM VENTING MEANS” issued on May 19, 1987 to Monte J. Solazzi; U.S. Pat. No. 4,698,210 entitled “SAMPLE CUP APPARATUS FOR USE IN X-RAY SPECTROSCOPY EMPLOYING SELECTIVELY OPERATED VENTING MEANS” issued on Oct. 6, 1987 to Michael C. Solazzi; U.S. Pat. No. 5,451,375 entitled “APPARATUS FOR TRIMLESS SAMPLE CUP USED IN X-RAY SPECTROSCOPY” issued on Sep. 19, 1995 to Monte J. Solazzi; U.S. Pat. No. 5,454,020 entitled “SAMPLE CUP ADAPTED FOR UPRIGHT HORIZONTAL AND INCLINED SAMPLE PLANE GEOMETRY SYSTEMS” issued on Sep. 26, 1995 to Monte J. Solazzi; and U.S. Pat. No. 5,630,989 entitled “APPARATUS FOR TRIMLESS SAMPLE CUP USED IN X-RAY SPECTROSCOPY” issued on May 20, 1997 to Monte J. Solazzi.
During spectrochemical analysis it is essential for the surface of thin film material, which covers an open top of the cell body, to remain planar in order to produce reliable data. The area of the thin film material that covers the top of the cell body is known as the sample surface plane. During the spectrochemical analysis of certain specimens that exhibit high abrogation in air, the sample cup containing a specimen may be placed within a vacuum or inert gas environment. Under conditions where pressure equalization is not implemented, the thin film of material covering the sample will distend or bow outwardly due to the differential in pressures between the area within the sample cup and the environment surrounding the sample cup, which effect places portions of the thin film of material closer to the source of excitation. The variation in distance from the sample plane to the source of excitation, alters the intensity of the characteristic radiation of the specimen and also alters the intensity of radiation impinging upon the sample specimen from the excitation source. Consequently, the spectrochemical analysis may produce erroneous quantitative data. For applications in a gaseous environment where pressure is greater on the outside of the sample cup than within the sample cup, the thin film of material distends or is drawn into the hollow of the sample cup providing a concave sample surface, which effect increases the distance between the sample plane and the excitation source and results in erroneous analytical data.
In order to equalize pressure and eliminate distension of the sample surface plane, some sample cups are provided with a venting means. The venting means may be activated to provide pressure equalization between the inside and outside of the cup. Other sample cup designs include a main cell component with both ends opened. This double open-ended cup allows for attachment of the thin film sheet prior to the introduction of the sample. This design is useful for applications in an environment where continuous venting is desired from the moment of sample introduction.
In some situations, the spectroscopic analysis may be conducted in a vacuum or pressurized inert gas environment. In order to equalize the pressure between the inside and outside of the sample cups, some of these prior art sample cups have a vent hole. In addition, those prior art sample cups with the vent hole have the reservoir space on the exterior surface of the sample cups for catching any specimen material that may overflow out of the vent holes. However, because these reservoir spaces are provided on a cap or a cap-like structure that encloses the sample cup, if the sample cup is to be left open during the spectrochemical analysis without the cap, the reservoir is no longer available.
Thus, there is a need for an improved sample cup that may be placed in the spectrochemical analysis chamber with its top end open and still having a reservoir space to accommodate overflowing sample material during the spectrochemical analysis.